Free Engineering Tool
Motor Starting Current Calculator
Calculate motor starting (inrush) current for DOL, star-delta, soft starter, and VFD methods. Istart = kstart × Irated.
Results
Rated Current
Starting Current
Starting Methods Comparison
| Method | Current Multiplier | Torque | Typical Use |
|---|---|---|---|
| DOL | 6–8 × Irated | Full | Small motors < 7.5 kW |
| Star-Delta | 2–3 × Irated | ~33% | Pumps, fans, 7.5–75 kW |
| Soft Starter | 2–4 × Irated | Variable | Conveyors, compressors |
| VFD | 1–1.5 × Irated | Full | Any, best control |
Given: P = 15 kW, V = 400 V, cos φ = 0.85, η = 0.91, DOL k = 7
Irated = 15000 / (√3 × 400 × 0.85 × 0.91) = 28.0 A
Istart = 7 × 28.0 = 196.0 A
Professional field balancing instruments and software. Used in 50+ countries.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
